Abstract: The purpose of the study is to explore the regulation mechanism of castor seed germination under low temperature, in order to select and breed new varieties with high quality and resistance. In this study, three castor cultivars were used as materials. A complete randomized design was adopted with 3 duplicates. The low temperature of 15℃ and normal temperature of 25℃ (CK) were set up and the seeds germination experiments were conducted. After determining the vitality of cultivars, the physiological index was determined by taking samples when the radicles were 2 cm long. The results indicated that seeds germination of castor was significantly hindered by low temperature stress. The sugar content and TSP were less than that of the control in radicles under low temperature, but the MDA content was significantly higher than that of the control under the low temperature. The performance of enzyme activity in castor was quite different under low temperature, SOD activity in radicles was less than that of the control under low temperature. Excepting‘Tongbi No.6’, other varieties’POD activity was significantly lower than that of the control; the CAT activity performance was not significant, and the activities were basically coincident under different temperature conditions. It concluded that‘Tongbi No.5’performed well under low temperature stress, and it could take gene sequencing for the next step.